Gyroscope damping device



Jan- 26, 1954 B. J. BAECHER GYROSCOPE DAMPING DEVICE Filed Augx! 25. 195

n relillnw Patented Jan. 26, i954 CFFICE 6 Claims. (Cl. 74-5.5)

(Granted under Title 35, U. S. Code (19521).,

sec. 266) i v rihe invention described herein may be manufactured andused by or for the Government of the United States of America forgovernmental purposes Without the payment of any royalties thereon ortherefor.

This invention relates o improvements in gyrO- scopes, and moreparticularly pertains to improvements in gyroscope damping devices.

The pendulum ballistic, the controlling element I that makes thesensitive element of a gyro-compass north seeking, is an invertedpendulum in conventional gym-compass such as the Sperry Gyro-CompassMark 18, Model 3. The unit consists essentially of an inverted pendulumWeight that maintains the azimuth alignment and -a repulsion magnetarrangement that -damps any oscillations of the gyro about the meridian.The pendulum is a weight that is located laround the north rotor bearinghousing, said Weight being supported by two semi-circular flat springssecured at one end to the rotor case. If the compass deviates from itstrue north position, the rotation of the earth will cause the rotor totilt. The Weight then will take up a position such that a torque isapplied about the horizontal axis of the gyro. This torque causes thegyro to precess about its vertical axis to bring the compass back on themeridian. A metal plate or paddle, that moves in a directionperpendicular to its length in a vessel containing a viscous iluid isattached to the Weight. This arrangement damps out oscillations of theweight caused by roll or pitch of the ship. Tv/o repulsion magnets areused to provide torque about the vertical axis of the gyro to dampenoscillations of the compass 'about the meridian.

There are .several disadvantages to the Weight damping system abovedescribed. The movement of the 'paddle in a direction perpendicular toits length through a very viscous uid provides a combination of viscousfriction fand spring action, there being a force opposing the motionproportional to the displacement caused by the fluid piling up in frontof the paddle and acting like a compression-type spring. introduced thepossibility of the pendulum being held out from the vertical by the uid.Finally, the clearance between the supporting springs and the Weight andthe limit stops in the damper attached to the Weight restrict the motionof the Weigh to such an extent as to prevent application of the correctballistic ydeflection under many operating conditions.

The foregoing disadvantages are overcome substantially by the subjectdevice, which prof In addition, there is Y 2 vides improved viscousdamping of the pendulum, renders negligible the amount the pendulum isheld out of the vertical by the damping suspension, minimizescompression forces in the viscous fluid, `and provides ample clearances.

Generally, the damping system of the subject device provides a pluralityof paddles moving in a direction parallel to their length through aplurality of troughs of damping fluid interconnected at their bottom.The direction of motion of the paddles, parallel to their length,provides almost pure shearing forces in the fluid, 'thereby providingretarding forces proportional to the velocity of movement of the paddles'through the vfluid and also reducing compression eiiects in the fluidand the tendency to hold the pendulum out yoi the vertical to anegligible amount.

n addition, with the pendulum-type suspension of the ballistic weight,the motion of 'the paddles is directly proportional to the motion of thecenter of gravity of the weight, so that uniform damping is obtained.Further, the employment of silicone as 'a damping fluid makes the effectoi temperature variations on damping negligible, by reason of the loWtemperature coeflicient of viscosity of such fluid. The viscosity of thefluid employed .retards the swing out of the -ballistic weight on shortswings such as are obtained due to roll and pitch to a sufficient amountto minimize intercardinal rolling error but still permits the pendulumto swing out the proper amount to provide the correct ballisticdeflection on high .speed turns.

The gym-compass damping structure disclosed .incorporates clearancessuicient to permit response toas much plus or minus shift in the dynamicvertical as might be met under operating conditions, and .also providesfor .linear motion of the weight on northerly accelerations.

Accordingly, it isa principal object of this invention to provideimproved structure for damping the ballistic Weight of a gym-compass.

Another object is to provide improved damping structure forgym-Compasses, such structure be- .ing characterized by viscous dampingof the pendulum, the elimination of the tendency of the pendulum to beheld out of the vertical .by the ldamping suspension, or the renderingof such factor negligible, and the minimization o1 .compression forcesin the viscous damping fluid.

Still another object is to provide, in a gyrocompass, a pendulous Weightcarrying a paddle that moves in a damping fluid in a direction parallelto its length to provide almost pure shearing forces in the uid, so thatthe retarding forces 3 are proportional to the velocity of movement ofthe paddle through the fluid and so that compression effects in thefluid and the tendency of the nuid to hold the pendulum out of verticalare reduced to a negligible amount.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

Fig. 1 is an elevation of a damping device for a gyro-compass, shownpartly in section, and showing the gyro-compass rotor case and bearingin phantom, illustrating a preferred embodiment of the invention;

Fig. 2 is a section taken on the line 2-2 of Fig. 1, showing extendedpositions of the damping structure in broken lines;

Fig. 3 is a section taken on the line 3-3 of Fig. 1;

Fig. 4 is a plan view of the support member of the device; and

Fig. 5 is a plan view of the paddle-bracket member of the device.

Similar numerals refer throughout the several views.

The support member comprises a first leg portion I3 having a pluralityof bores I5 carrying screws I1 whereby said support is secured to therotor case |9 of a gyro-compass, a body-plate portion 2| adapted to lieflush with said rotor case, and a second leg portion 23 extendingoutwardly from said rotor case normal to said bodyto similar parts plateportion. Arms 25 extend laterally from each side of said leg portion 23,and the end of each arm is provided with a slot 21 and a cross-bore 29that is threaded to receive a screw 3|, said slot and bore providingmeans to secure a flexible wire 33 that depends therefrom to provide aflexure type hinge. A bore 35 medial the forward portion of the legportion 23 carries a fulcrum pin 31, said bore 35 being counterbored atboth the upper and lower faces of said leg portion to permit said pin torock in the manner hereinafter described.

Bracket 39 is an L-shaped plate having a plurality of bores in one legaligned axially with the axes of the wires 33 and bore 35. The pin 31 issecured in one of said bores, as by tack welding of said pin to saidleg, and the other of said bores are threaded to carry a wire-guidingassembly comprising nuts having axially tapered bores 41. The netherends of wires 33 are secured by the lugs 49 that have axial bores thatreceive said wires and hold said wires by means of the setscrews 5|. Thelugs 49 are secured to the nether face of spring 4| as by tack weldingand the spring 4| is attached to the nether leg of bracket 39 by screws43. Spring 6| is provided to prevent kinking of the suspension wires 33by keeping such wires under tension at all times.

Weight 53 is a lead annulus having a central opening of suiiicientdiameter to clear the protuberant portion of the bearing of rotorhousing I9 when said weight is secured dependingly from bracket 39. Thelower portion of said weight is of reduced thickness, as shown in Fig.2, to increase the angular limit of swing thereof, as hereinafterdescribed.

Gasket 55 and cap plate 51 are secured'to the rotor bearing 59 by meansof a plurality of Screws 6| countersunk to lie flush with the face ofsaid cap plate. Screws 0| and nuts 'E1 581V@ i@ Secure bracket 19 toweight 53. The said weight 53 is also secured to bracket 39 by screws 85and nuts 81.

A plurality of paddles 89 are secured to and depend from the legs 9|formed in the horizontally disposed portion of bracket 10, said paddleshaving their faces arranged in parallel spaced relation for movement inthe plane of said faces.

Stud S3 'and bracket e5 are secured to the rotor case I9 by screws 91.Said bracket 95 carries trough 99, which is subdivided into a pluralityof compartments by spacer plates |01, communication of the fluid |03between compartments being permitted through the slot |05 formed by thelower portion of each of said plates |01 and the floor of said trough.The spacer plates are so arranged that one of said paddles 89 can travelin the fluid in each of said compartments.

The damping fluid |03 is preferably a silicone fluid, which ischaracterized by its small temperature coemcient of viscosity, it beingdesirable to prevent variations in temperature from having an effect onthe damping. Such fluid is of sufcient viscosity to retard the swing outof the ballistic weight on short swings, such as are obtained due toroll and pitch, to a sulcient amount to minimize intercardinal rollingerror, but is not of such high viscosity as to prevent the pendulum fromswinging out the proper amount to provide the correct ballisticdeflection on high speed turns. A preferred fluid is Corning DC siliconeFluid No. 200, which has a viscosity at 25 C. of 200,000 centistokesrI'he wire-suspended pendulum hereinabove described tends to hang in thedynamic vertical, shown by the broken line |01 of Fig. 2.

The paddles 89 move through the fluid |03 in a direction parallel totheir lengthin the plane of the faces of said paddlesand thereby providealmost pure shearing forces in the fluid. As a result, said paddlesprovide retarding forces proportional directly to the velocity of theirmovement through the fluid. Such orientation of the paddles also reducesto a negligible amount the compression effects in the fluid and thetendency of the fluid to hold the pendulum out of the vertical. Trueviscous damping, with changes in temperature having a negligible effectbecause of the small temperature coefficient of viscosity of the fluidemployed, is therefore realized.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. The invention disclosedherein is applicable to gyroscopc stable verticals and like devices. Thedamping can be varied by varying the spacing of the paddles, the numberand size of the paddles, and the Viscosity of the fluid. The suspensionmeans can be a wide range -of equivalent devices. Other modificationsand changes suggest themselves readily to those skilled in the art.Accordingly, it is to be understood that within the scope of theappended claims the invention may be practiced otherwise than asspecifically described.

I claim:

1. In a gyro compass having a rotor case and a ballistic Weight carriedby said case, a damping device comprising a trough mounted on said rotorcase, a viscous fluid carried in said trough, and a plurality of paddleseach having opposed planar faces, said paddles being mounted on saidweight in spaced and parallel relation and mov- 15 able in said uid inthe planes of said faces.

Y 2. In a gyro compass having a rotor case and a ballistic Weightcarried by said case, a damping device comprising a trough having aplurality of compartments, said trough being mounted on said rotor case,a viscous fluid carried in said compartments, and a plurality of paddleseach having opposed planar faces, said paddles being mounted on saidWeight in spaced and parallel relation and movable in said uid in theplanes of said faces.

3. In a gyro compass having a rotor case and a ballistic Weight carriedby said case, a damping device comprising a trough having a plurality ofcommunicating compartments, said trough being mounted on said rotorcase, a viscous iiuid carried in said compartments, and a plurality ofpaddles each having opposed planar faces, said paddles being mounted onsaid weight in spaced and parallel relation and movable in said iluid inthe planes of said faces.

4. In a gyro compass having a rotor case and a ballistic Weight carriedby said case, a damping device comprising a trough, a plurality ofslotted plates subdividing said trough into a plurality of communicatingcompartments, means to mount said trough on said rotor case, a viscousuid carried in said compartments, and a plurality of paddles each havingopposed planar faces, said paddles each being mounted on said weight inrelatively spaced and parallel relation and movable in said uid in oneof said compartments in the planes of said faces.

5. In a gyro compass having a rotor case and a ballistic weight carriedby said case, a damping device comprising a trough, a plurality ofplates subdividing said trough into a plurality of compartments, thenether portion of said plates and the iloor of said trough dening slots,means to mount said trough on said rotor case, a viscous fluid carriedin said compartments, and a plurality of paddles each having opposedplanar faces, said paddles being mounted on said weight in relativelyspaced and parallel relation, at least one of said paddles being movablein said uid in each of said compartments in the planes of said faces.

6. In a gyro compass having a rotor case and a ballistic weight carriedby said case, a damping device comprising a trough, a plurality ofplates subdividing said trough into a plurality of compartments, thenether portion of said plates and the floor of said trough dening slots,means to mount said trough on said rotor case, a viscous fluidcharacterized by small change in viscosity with change in temperaturecarried in said compartments, and a plurality of paddlesA each havingopposed planar faces, said paddles being mounted on said weight inrelatively spaced and parallel relation, at least one of said paddlesbeing movable in said fluid in each of said compartments in the planesof said faces.

BERNARD J. BAECHER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,291,695 Perry et al. Jan. 14, 1919 1,773,412 Thompson Aug.19, 1930 2,158,048 Braddon May 9, 1939 2,257,730 Braddon Oct. 7. 19412,464,516 Kenyon Mar. 15, 1949

